The purification of waste water or other fluids can be accomplished by feeding the fluid under pressure against membranes arranged in a stack, with pure water or other permeate passing through the membranes for recovery while the rest of the fluid, or concentrate, is also removed from the stack. It is well known that rapid rotation of the stack produces the desirable result of creating centrifugal forces that pressurize the feed fluid, helps in the radial outflow of permeate that has passed through the membranes, and helps sweep away material that could block the membranes. U.S. Pat. No. 4,025,425 by Croopnick et al describes apparatus of this type.
A commercial centrifugal purification apparatus may include perhaps three hundred membrane packs arranged in a stack within a rotor frame. When there is a considerable decrease in membrane pack efficiency, as where the membrane pores have been largely blocked, or where there is substantial leakage in the packs, several membrane packs or the entire stack may have to be replaced. With current designs, this requires removing the rotor frame from its bearings, removing a shroud and end plate from the rotor frame to gain access to the membrane stack, removing the membrane packs from the rotor, and installing a new group of membrane packs. Currently, it requires about two days to replace the membrane packs. A large part of the labor is involved in accurately aligning the membrane packs with the axis of the rotor frame, mounting the rotor frame on its bearings, and checking the rotatable fluid seals that connect rotatable pipes on the frame to stationery pipes. Not only is there considerable cost for services in replacing the membrane packs, but the equipment is shut down for perhaps two days, which can disrupt operations dependent upon the filtration apparatus. A rotary filtration apparatus which facilitated replacement of membrane packs, so they could be replaced in a much shorter period of time than at present, would be of considerable value.